1 | /* Emergency actions in case of a fatal signal. |
2 | Copyright (C) 2003-2004, 2009-2019 Free Software Foundation, Inc. |
3 | Written by Bruno Haible <bruno@clisp.org>, 2003. |
4 | |
5 | This program is free software: you can redistribute it and/or modify |
6 | it under the terms of the GNU General Public License as published by |
7 | the Free Software Foundation; either version 3 of the License, or |
8 | (at your option) any later version. |
9 | |
10 | This program is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
13 | GNU General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU General Public License |
16 | along with this program. If not, see <https://www.gnu.org/licenses/>. */ |
17 | |
18 | |
19 | #ifdef __cplusplus |
20 | extern "C" { |
21 | #endif |
22 | |
23 | |
24 | /* It is often useful to do some cleanup action when a usually fatal signal |
25 | terminates the process, like removing a temporary file or killing a |
26 | subprocess that may be stuck waiting for a device, pipe or network input. |
27 | Such signals are SIGHUP, SIGINT, SIGPIPE, SIGTERM, and possibly others. |
28 | The limitation of this facility is that it cannot work for SIGKILL. |
29 | |
30 | Signals with a SIG_IGN handler are considered to be non-fatal. The |
31 | functions in this file assume that when a SIG_IGN handler is installed |
32 | for a signal, it was installed before any functions in this file were |
33 | called and it stays so for the whole lifetime of the process. */ |
34 | |
35 | /* Register a cleanup function to be executed when a catchable fatal signal |
36 | occurs. |
37 | |
38 | Restrictions for the cleanup function: |
39 | - The cleanup function can do all kinds of system calls. It may also |
40 | modify (clobber) errno. |
41 | - It can also access application dependent memory locations and data |
42 | structures provided they are in a consistent state. One way to ensure |
43 | this is through block_fatal_signals()/unblock_fatal_signals(), see |
44 | below. Another - more tricky - way to ensure this is the careful use |
45 | of 'volatile'. |
46 | However, |
47 | - malloc() and similarly complex facilities are not safe to be called |
48 | because they are not guaranteed to be in a consistent state. |
49 | - Also, the cleanup function must not block the catchable fatal signals |
50 | and leave them blocked upon return. |
51 | |
52 | The cleanup function is executed asynchronously. It is unspecified |
53 | whether during its execution the catchable fatal signals are blocked |
54 | or not. */ |
55 | extern void at_fatal_signal (_GL_ASYNC_SAFE void (*function) (int sig)); |
56 | |
57 | |
58 | /* Sometimes it is necessary to block the usually fatal signals while the |
59 | data structures being accessed by the cleanup action are being built or |
60 | reorganized. This is the case, for example, when a temporary file or |
61 | directory is created through mkstemp() or mkdtemp(), because these |
62 | functions create the temporary file or directory _before_ returning its |
63 | name to the application. */ |
64 | |
65 | /* Temporarily delay the catchable fatal signals. |
66 | The signals will be blocked (= delayed) until the next call to |
67 | unblock_fatal_signals(). If the signals are already blocked, a further |
68 | call to block_fatal_signals() has no effect. */ |
69 | extern void block_fatal_signals (void); |
70 | |
71 | /* Stop delaying the catchable fatal signals. */ |
72 | extern void unblock_fatal_signals (void); |
73 | |
74 | |
75 | /* Return the list of signals that block_fatal_signals/unblock_fatal_signals |
76 | would block or unblock. |
77 | Fills signals[0..count-1] and returns count. */ |
78 | extern unsigned int get_fatal_signals (int signals[64]); |
79 | |
80 | |
81 | #ifdef __cplusplus |
82 | } |
83 | #endif |
84 | |